1. Field of the Invention
The invention relates to the production of asymmetrical laminated glazings made of a monolithic or laminated rigid support and a flexible plastic sheet having the desired properties. More particularly, the invention relates to the assembly of the flexible plastic sheet with the rigid support, as well as a prefabricated continuous ribbon comprising the flexible plastic sheet, used for the assembly.
The assembly of the rigid support with the flexible sheet to constitute the laminated glazing is generally performed by a preliminary pressing of the support with the sheet by calendering, followed by an autoclave cycle bringing into play the temperature and pressure which improves adhesion between the constituent elements and thus assures a final assembly.
2. Discussion of the Background
In European publication 0 015 209 a device has already been proposed comprising lower pressing means, particularly a series of rollers placed beside one another, upper pressing means comprising a flexible cylindrical pressing roller, extending over a length at least equal to the width of the elements to be assembled, this flexible roller being held in the desired curvature by upper means pressing on it, all of the pressing elements being mounted on a pivoting frame.
The flexible sheet which is assembled with the rigid support by using this device must be presented in the form of a continuous ribbon to be able to be held in the desired position for the assembly which is performed while advancing.
Unfortunately, in this type of assembly while advancing, it is not possible to present the rigid supports to be coated one after another without separation intervals, especially when it involves glazings curved in the direction of advance which corresponds generally to the curvature in the direction of the length of the glazing. In this case, the assembly operation uses the rocking of the frame pivoting as the glazing advances between the pressing elements, to assure a pressing that is approximately perpendicular to the surface of the glazing during the entire operation.
The position of the frame pivoting at the output of a glazing is generally symmetrical in relation to a plane vertical to the position of the rocking frame at the input of a glazing, so that between the output of one glazing and the input of the next glazing, the frame must rock in the other direction to come back to its start of assembly position.
It is therefore necessary to separate two consecutive rigid supports by an interval at least equal to the distance which corresponds to the advance of the glazings during the return rocking time of the frame. This interval therefore corresponds also to a loss of flexible sheet material.
Further, in the case of automobile glazings, the developed surface of the glazing exhibits an approximately trapezoidal shape which causes other losses of flexible sheet, in particular the entire portion between the contours of the trapezoid that is called a blank and the rectangle in which the blank is inscribed.
The various losses of material can, in total, constitute about 30% of the surface of the sheet.